It is known in the art to determine the speed of a pump motor using dedicated speed sensors. Given a clocked operation of a pump motor, the speed of the pump motor may also be ascertained, in the undriven phase, on the basis of the generating voltage of the pump motor. Such methods are used in the regulation of the pump motor within the framework of an electrohydraulic braking system, for example.
German Patent 41 33 269 describes a method for measuring the speed of a rotating part surrounded by a housing, in which a further signal that is a function of the speed is detected, and this further signal is filtered and digitalized, as well as Fourier-transformed twice. The speed is ascertained from the spectrum thus obtained, by evaluating the absolute maximum. A relatively great computing power is necessary to implement such a speed measurement because of the Fourier analysis used.
In general, known methods for detecting the speed of motors, particularly pump motors, tend to be relatively costly.